Solid Fuel Grade Gasification-Combustion Dual Bed Poly-Generation System and Method Thereof

Abstract

The present invention demonstrates a solid fuel grade gasification-combustion dual bed poly-generation system, comprising a combustion system, a gasification system, a synthesized gas cooling and purifying system and a synthesized gas methanization system. The combustion system is connected with the gasification system through a circulating material return system. The gasification system mainly adapts the circulating fluidized-bed combustion mode. The gasification system adapts the fluidized-bed incomplete gasification method and the generated semi-coke is returned to the combustion system for re-utilization. The synthesized gas purifying and cooling unit adapts water cycling and combustible recycling. The by-products, CO.sub.2 and steam, in the methanization unit can be recovered, so the maximum utilization rate of energy in this system is realized.

Claims

1. A solid fuel grade gasification-combustion dual bed poly-generation system, characterized by comprising a circulating fluidized-bed combustion boiler (1), a circulating fluidized-bed gasification boiler (2), a synthesized gas purification unit and a methanation unit; the bottom of the circulating fluidized-bed combustion boiler (1) is provided with a combustion boiler slag outlet (7) and a combustion boiler fluidizing air inlet (5); the fluidizing air enters the combustion boiler fluidizing air inlet (5) and then flows to the circulating fluidized-bed combustion boiler (1) via a combustion boiler air distribution unit (6a), one part of the fuel enters the circulating fluidized-bed combustion boiler (1) via a combustion boiler fuel feeding opening (4a), flue gas generated during combustion enters at least a primary combustion boiler cyclone separation unit via a gas channel (8), the gas after separation is directly exhausted, while separated ash particles are returned back into the circulating fluidized-bed combustion boiler via a combustion boiler material return unit (10a), the heat generated during combustion is used to produce combustion boiler steam (46a) and the steam (46a) from combustion boiler is used for external supply and is supplied to the circulating fluidized-bed gasification boiler (2); the bottom of the circulating fluidized-bed gasification boiler (2) is provided with a semi-coke outlet (49) and gasification boiler fluidizing air inlets (11a, 11b). A gasifying agent for gasification is sent into the gasification boiler fluidizing air inlets (11a, 11b) and then flows into the circulating fluidized-bed gasification boiler (2) via a gasification boiler air distribution unit (6b), steam (44) in the gasifying agent comes from a combustion boiler steam (46a) and/or methanization unit, carbon dioxide is the carbon dioxide generated by the methanization unit, the other part of the fuel is fed into the circulating fluidized-bed gasification boiler (2) via a gasification boiler fuel feeding opening (4b), the semi-coke generated by gasification is discharged via a semi-coke outlet (49) and then sent into the combustion boiler fuel feeding opening (4a), the synthesized gas enters at least a primary gasification cyclone separation unit via a synthesized gas outlet on top of the circulating fluidized-bed gasification boiler, after separation the synthesized gas is sent into a synthesized gas purification unit, while the separated ash particles are sent back into the circulating fluidized-bed gasification boiler (2) and/or the combustion boiler fuel feeding opening (4a) via a gasification boiler material return unit (10b), the synthesized gas purification unit primarily washes and de-dusts the synthesized gas, uses water as a cooling media to chill the synthesized gas in a heat exchange mode, sends the cooled gas to the methanization unit, performs oil-water separation on at least one part of the sewage generated during cooling, and sends impurities expelled from the separation to the combustion boiler fuel feeding opening (4a) or the gasification boil fuel feeding opening (4b) or sends by-products obtained for further processing; the methanization unit converses the fed synthesized gas into synthesized natural gas through low-temperature methanol washing process and methanization process, sends carbon dioxides generated in the low-temperature methanol washing process to the gasification boiler fluidizing air inlets (11a, 11b) and the steam (44) as a side produced by the methanization process to the gasification boiler fluidizing air inlets (11a, 11b), or as a supplemental steam required by the methanization unit or discharges the stream for other purposes.

2. The solid fuel grade gasification-combustion dual bed poly-generation system according to claim 1, characterized in that, the gasification boiler cyclone separation unit is a two-class cyclone separation structure consisting of a primary cyclone separator (3b) and a secondary cyclone separator (3c), wherein the ash particles expelled by the primary cyclone separator (3b) are sent back into the circulating fluidized-bed gasification boiler (2) through the gasification boiler material return unit (10b), and those particles expelled by the secondary cyclone separator (3c) are sent back into the combustion boiler fuel feeding opening (4a).

3. The solid fuel grade gasification-combustion dual bed poly-generation system according to claim 1, characterized in that, the circulating fluidized-bed gasification boiler (2) is also provided with side gasifying agent inlets (11c, 11d), the side gasifying agent inlets (11c, 11d) are located above the gasification boiler fluidizing air inlets (11a, 11b), wherein oxygen and steam are sent into the side gasifying agent inlets (11c, 11d).

4. The solid fuel grade gasification-combustion dual bed poly-generation system according to claim 1, characterized in that, the steam generated in the process that the synthesized gasification unit chills the synthesized gas is led to the gasification boiler fluidizing air inlets (11a, 11b).

5. The solid fuel grade gasification-combustion dual bed poly-generation system according to claim 1, characterized in that, the synthesized gas purification unit comprises a cooling scrubber (16), a heat recovery boiler (19), a cooling unit (22), a first oil-water separator (25), a second oil-water separator (26) and a sewage settlement tank (36); the synthesized gas coming from the gasification boiler cyclone separator unit is sent into the cooling scrubber (16) or the heat recovery boiler (19), when the synthesized gas is sent into the cooling scrubber (16), the cooling scrubber (16), the heat recovery boiler (19) and the cooling unit (22) are connected in turn, wherein the cooling scrubber (16) primarily washes, de-dusts and chills the synthesized gas and then the cooled synthesized gas is sent into the heat recovery boiler (19), the heat recovery boiler (19) is also supplied with de-salted water (55) simultaneously, the de-salted water (55) exchanges heat with the synthesized water in the heat recovery boiler (19) and then as a cooling water is led to the cooling scrubber (16), the synthesized gas enters the cooling unit (22) after the heat exchange, the cooling unit (22) receives supernatant (38) as a cooling media from the sewage settlement tank (36) simultaneously, the synthesized gas flows out of the cooling unit (22) and then is sent into the methanization unit, the sewage expelled from the heat recovery boiler (19) and the cooling unit (22) in the heat exchange process is sent to the first oil-water separator (25) and the second oil-water separator (26) through respective pipes, the first oil-water separator (25) and the second oil-water separator (26) as well as the sewage settlement tank (36) are connected in turn, a part of the sewage undergoes separation in the first oil-water separator (25), the obtained product as a washing water is led to the cooling scrubber (16), and the impurities expelled by the first oil-water separator (25) and the second oil-water separator (26) are sent to the combustion boiler fuel feeding opening (4a) or sent to the gasification boiler fuel feeding opening (4b) or as side products are used for further process, a part of the sewage passes through the first oil-water separator (25) and the second oil-water separator (26) and then is collected in the sewage settlement tank (36), the supernatant (38) produced by the sewage settlement tank (36) is sent to the cooling unit (22), residual deposits (37) are sent out of the area for further process, and the rest of which is sent out of the area for sewage treatment (52), when the synthesized gas is sent into the heat recovery boiler (19), the heat boiler (19), the cooling scrubber (16) and the cooling unit (22) are connected in turn; the heat recovery boiler (19) is supplied with de-salted water (55) and supplied with the synthesized gas from the gasification boiler cyclone separation unit simultaneously, the de-salted water (55) exchanges heat with the synthesized water in the heat recovery boiler (19) to form steam, which as a gasifying agent is sent into the gasification boiler fluidizing air inlets (11a, 11b), after heat exchange, the gasifying agent is sent into the cooling scrubber (16), the cooling scrubber (16) primarily washes, de-dusts and chills the fed synthesized gas and then the cooled synthesized gas is sent into the cooling unit (22), the cooling unit (22) is also supplied with a supernatant (38) as a cooling media from the sewage settlement tank (36) simultaneously and the synthesized gas flows out of the cooling unit (22) and then is sent into the methanization unit, the sewage produced by the cooling scrubber (16) and the cooling unit (22) in the heat exchange process is sent to the first oil-water separator (25) and the second oil-water separator (26) through respective pipes the first oil-water separator (25) and the second oil-water separator (26) as well as the sewage settlement tank (36) are connected in turn, a part of the sewage is separated by the first oil-water separator (25) and the product as the washing water is led to the cooling scrubber (16). The impurities expelled by the first oil-water separator (25) and the second oil-water separator (26) are sent to the combustion boiler fuel feeding opening (4a) or sent to the gasification boiler fuel feeding opening (4b) or as by-products are used for further process, a part of the sewage passes through the first oil-water separator (25) and the second oil-water separator (26) and then is collected in the sewage settlement tank (36), the supernatant (38) produced by the sewage settlement tank (36) is sent to the cooling unit (22), and deposits (37) accumulated are sent out of the area for processing and the rest of which is sent out of the area for sewage treatment (52).

6. The solid fuel grade gasification-combustion dual bed poly-generation system according to claim 5, characterized in that, when the synthesized gas is sent into the cooling scrubber (16), the heat recovery boiler (19) is connected to the first oil-water separator (25) through the heat exchanger (20).

7. The solid fuel grade gasification-combustion dual bed poly-generation system according to claim 5, characterized in that, when the synthesized gas is sent into the cooling scrubber (16), the exit temperature of the synthesized gas after flowing through the cooling scrubber (16) is 150° C.-250° C., the exit temperature of the synthesized gas after passing through the heat recovery boiler (19) is 120° C.-180° C.; the exit temperature after passing through the cooling unit (22) is 25° C.-45° C.

8. The solid fuel grade gasification-combustion dual bed poly-generation system according to claim 5, characterized in that, the methanization unit comprises of a shift reaction unit (39), a low-temperature methanol washing unit (41) and a methanization unit (43), the synthesized gas flows through the shift reaction unit (39), the low-temperature methanol washing unit (41) and the methanization unit (43) in turn to form the synthesized natural gas, the carbon dioxide generated by the low-temperature methanol washing unit (41) is sent to the gasification boiler fluidizing air inlets (11a, 11b) and the steam (44) side produced by the methanization unit (43) is sent to the gasification boiler fluidizing air inlets (11a, 11b), or as a supplemental steam required by the methanization (39) or is discharged for other purposes.

9. A poly-generation method for the solid fuel grade gasification-combustion dual bed poly-generation system according to claim 1, characterized by the following steps: step 1): dividing fuel into two parts, sending one part into the combustion boiler fuel feeding opening (4a) and the other into the gasification boiler fuel feeding opening (4b), discharging the slag produced by combustion in the circulating fluidized-bed combustion boiler (1) from the combustion boiler slag outlet (7) and the gas generated is expelled from the top, where a part of the particles entrained in the gas are separated by the combustion boiler cyclone separation unit, the separated particles are sent into the circulating fluidized-bed combustion boiler (1) through the combustion boiler material return unit (10a) for further combustion the steam produced by the circulating fluidized-bed combustion boiler (1) is used for power generation, central heating and other purposes, the circulating fluidized-bed combustion boiler (1) adapts air as the fluidizing air and oxidant; step 2): discharging semi-coke produced by the circulating fluidized-bed gasification boiler (2) in the gasification process from the semi-coke outlet (49) back to the circulating fluidized-bed combustion boiler (1) for further combustion, discharging the synthesized gas from the top, collecting a part of particles entrained in the synthesized gas by the gasification boiler cyclone separation unit, sending the particles back into the circulating fluidized-bed gasification boiler (2) through the gasification boiler material return unit (10b) for further utilization or back to the circulating fluidized-bed combustion boiler (1) for combustion; step 3): primarily washing and de-dusting the synthesized gas, using water as a cooling media to chill the synthesized gas in a heat exchange mode and sending the cooled gas to the methanization unit by the synthesized gas purification unit, performing oil-water separation on at least one part of the sewage generated during cooling, sending impurities emitted from the separation to the combustion boiler fuel feeding opening (4a) or the gasification boiler fuel feeding opening (4b) or for further deeper processing the at least a part of sewage as a side product; step 4): conversing the fed synthesized gas into synthesized natural gas through low-temperature methanol washing process and methanization process, sending the carbon dioxide generated in the low-temperature methanol washing process to the gasification boiler fluidizing air inlets (11a, 11b) and the steam (44), the side produced by the methanation process to the gasification boiler fluidizing air inlets (11a, 11b), or sending using it as a supplemental steam required by the methanization unit or to be expelled outside for other use

10. The poly-generation method for the solid fuel grade gasification-combustion dual bed poly-generation system according to claim 9, characterized in that, in step 2),the operating pressure of the circulating fluidized-bed gasification boiler (2) is 0˜8.0 MPa, and the exit temperature of the synthesized gas reaches 650□˜1,050□.

Description

DESCRIPTION OF SEVERAL VIEWS OF THE ATTACHED DRAWINGS

[0034] FIG. 1 is a schematic view of the solid fuel grade gasification-combustion dual bed poly-generation system without a gasifying agent inlet located one side of a gasification boiler.

[0035] FIG. 2 is a schematic view of the solid fuel grading gasification-combustion dual bed poly-generation system with a gasifying agent inlet located one side of a gasification boiler.

[0036] FIG. 3 is a schematic view of the heat recovery type solid fuel grading gasification-combustion dual bed poly-generation system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0037] To better understand the present invention is described in detail in combination with the attached drawings and preferred embodiments.

Embodiment 1

[0038] As shown in FIG. 1, this embodiment discloses a solid fuel grade gasification-combustion dual bed poly-generation system, comprising a circulating fluidized-bed combustion boiler 1, a circulating fluidized-bed gasification boiler 2, a synthesized gas purification unit and a methanization unit.

[0039] A fuel (in this embodiment, the fuel is one or mixture of solid fuels such as coal, gangue, petroleum coke and biomass) is divided in two parts and fed separately into the circulating fluidized-bed combustion boiler 1 and the circulating fluidized-bed gasification boiler 2 via a combustion boiler fuel feeding opening 4a and a gasification boiler fuel feeding opening 4b. An oxidant required to complete combustion in the circulating fluidized-bed combustion boiler 1 enters a combustion boiler air distribution unit 6a via a combustion boiler fluidizing air inlet 5 and then enters the circulating fluidized-bed combustion boiler. Ash produced in the combustion process of the fuel is discharged from a combustion boiler slag outlet 7. Flue gas generated during combustion flows into a cyclone separator 3a via a gas channel 8 and then is discharged from a top 9 thereof. The separated ash particles are sent back to the circulating fluidized-bed combustion boiler 1 through a combustion boil material feedback opening 10a. The heat generated in the combustion process is used to generate combustion boiler steam 46a. The combustion boiler steam 46a can be used for heating 46b, power generation 47 and delivered to the circulating fluidized-bed gasification boiler 2 via a pipe 46c.

[0040] A gasifying agent required to perform gasification by the circulating fluidized-bed gasification boiler 2 comes from the combustion boiler steam 46a delivered via the pipe 46c and the steam 44 of the methanization unit. The oxygen comes from an outside area 51 and carbon dioxide 53 comes from the methanization unit. The gasifying agent enters the circulating fluidized-bed gasification boiler 2 via gasification boiler fluidizing inlets 11a, 11b and a gasification boiler air distribution unit 6b. Semi-coke generated during gasification is discharged from a semi-coke outlet 49. Synthesized gas passes through a synthesized gas outlet 13, then is separated by a primary cyclone separator 3b and a secondary cyclone separator 3c and then enters a synthesized gas cooling and purifying unit. The primary cyclone separator 3b and the secondary cyclone separator 3c are connected with a synthesized gas guide pipe 14 there-between. The secondary cyclone separator 3c and the synthesized gas cooling and purifying unit are connected with a synthesized gas pipe 15 there-between. The ash particles separated by the primary cyclone separator 3b are sent back into the circulating fluidized-bed gasification boiler 2 via a gasification boiler material return unit 10b, and those separated by the secondary cyclone separator 3c are collected by a slag hopper 12 and then sent to the combustion boiler fuel feeding opening 4a or the gasification boiler fuel feeding opening 4b.

[0041] The synthesized gas purification unit comprises a cooling scrubber 16, a heat recovery boiler 19, a cooling unit 22, a first oil-water separator 25, a second oil-water separator 26 and a sewage settlement tank 36. In this embodiment, the cooling scrubber 16, the heat recovery boiler 19 and the cooling unit 22 are connected through synthesized gas pipes 18, 21 in turn. The cooling unit 22 is connected with the methanization unit through a synthesized gas pipe 23.

[0042] The synthesized gas first enters the cooling scrubber 16, is primarily washed, de-dusted and cooled then, and then enters the heat recovery boiler 19. Waste water 48 generated by the cooling scrubber 16 is discharged. The heat recovery boiler 19 is supplied with de-salted water simultaneously. The de-salted water absorbs a part of the heat of the synthesized gas and then as a scrubber cooling water is delivered to the cooling scrubber 16 via a circulating water pipe 17. A part of the heat of the synthesized gas is recovered by the de-salted water, and then the synthesized gas enters the cooling unit 22. The cooling unit 22 has a function of 1˜3-stages of classification cooling. The sewage generated by the heat recovery boiler 19 and the cooling unit 22 in the heat exchange process is delivered to the first oil-water separator and the second oil-water separator 26 through respective condensing pipes 24. The condensing pipe between the heat recovery boiler 19 and the first oil-water separator 25 is also provided with a heat exchanger 20. The first oil-water separator and the second oil-water separator 26 as well as the sewage settlement tank 36 are connected in turn through sewage pipes 34, 35. The oil-water separator performs oil-water separation on a part of the sewage, and then this part of sewage is delivered to the cooling scrubber 16 through the circulating water pipe 27. Impurities such as coal tar at el. emitted from the first oil-water separator 25 and the second oil-water separator 26 are partial combustible impurities which combustible constitution reaches 5% wt to 40% wt. Those combustible impurities are sent back into the circulating fluidized-bed combustion boiler 1 or the circulating fluidized-bed gasification boiler 2 via a system fuel mixing circuit 50 to be reused or as by-products are deposed for further deeper processing 31, 32. Since the sewage collected by the sewage settlement tank 36 has been preliminary treated, the generated supernatant 38 is returned back to the cooling unit 22 through the circulating circuit 38, some of which is delivered to the outside area for sewage treatment 52 and the residual deposit 37 delivered outside the area for treatment. The exit temperature of the synthesized water after passing through the cooling scrubber 16 is 150° C.-250° C.; the exit temperature of the synthesized gas after passing through the heat recovery boiler 19 is 120° C.-180° C.; and the exit temperature after passing through the cooling unit 22 is 25° C.-45° C.

[0043] After being cooled and de-dusted by the synthesized gas purification unit, the synthesized gas enters the methanization unit. In this embodiment, the methanization unit comprises a shift reaction unit 39, a low-temperature methanol washing unit 41 and a methanization unit 43 connected in turn. The shift reaction unit 39, the low-temperature methanol washing unit 41 and the methanization unit 43 are respectively connected through the synthesized gas pipes 40, 42 in turn. The synthesized gas undergoing the low-temperature methanol washing process and the methanization process has been finally conversed into the qualified artificial natural gas 45. The carbon dioxide 53 generated by the low-temperature methanol washing unit 41 in the low-temperature methanol washing process can be delivered to the circulating fluidized-bed gasification boiler 2 to serve as the gasifying agent or as a by-product for further deeper process 54. The steam, a by-product of the methanization unit 43 in the methanation process can be delivered to the circulating fluidized-bed gasification boiler 2 to serve as the gasifying agent or used for other purposes.

Embodiment 2

[0044] As shown in FIG. 2, this embodiment discloses a solid fuel grade gasification-combustion dual bed poly-generation system, different from embodiment 1 in that, in this embodiment, there are gasifying agent feeding openings 11c and 11d upon the demands of the gasification load and the coal type located near the circulating fluidized-bed gasification boiler 2. The oxygen and steam are sent to the said gasifying agent inlets 11c, 11d to strengthen the gasification reaction, expedite the tar decomposition in the gasification process and improve the gas generation rate of the system.

[0045] Other structures are identical with those in the embodiment 1.

Embodiment 3

[0046] As shown in FIG. 3, this embodiment is different from embodiment 1 in that:

[0047] First, the heat recovery boiler 19, the cooling scrubber 16 and the cooling unit 22 are connected in turn. The heat recovery boiler 19 is supplied with the de-salted water 55 and supplied with the synthesized gas from the secondary cyclone separator 3c simultaneously. The de-salted water 55 exchanges heat with the synthesized gas in the heat recovery boiler 19 to generate steam; the steam as a gasifying agent is sent into the gasification boiler fluidizing air inlets 11a, 11b. After the heat exchange, the synthesized gas is delivered into the cooling scrubber 16, the cooling scrubber 16 primarily washes, de-dusts and chills the fed synthesized gas and then the cooled synthesized gas enters the cooling unit 22. The sewage generated by the cooling scrubber 16 in the heat exchange process is sent to the first oil-water separator 25 through the condensing pipe 24. A part of the sewage undergoing the oil-water separation in the first oil-water separator 25 and then is led as the cooling water to the cooling scrubber 16 via the circulating water pipe 57.

[0048] Second, in the methanization unit, the shift reaction unit 39 needs steam and the steam 44 as a side product by the methanization unit in the methanization process is delivered to the shift reaction unit 39 via the pipe 58.

[0049] Other structures are identical with those in the embodiment 1.

[0050] The present invention provides a poly-generation method for the solid fuel grade gasification-combustion dual bed poly-generation system according to any one of embodiments, characterized by comprising the following steps of:

[0051] step 1): dividing fuel into two parts, sending one part into the combustion boiler fuel feeding opening 4a and the other into the gasification boiler fuel feeding opening 4b. The discharging slag produced by combustion in the circulating fluidized-bed combustion boiler 1 from the combustion boiler slag outlet 7 and flue gas generated is expelled from the top, where a part of particles entrained by the gas are separated by the combustion boiler cyclone separation unit. The separated particles are into the circulating fluidized-bed combustion boiler 1 through the combustion boiler material return unit 10a for further combustion. The steam produced by the circulating fluidized-bed combustion boiler 1 is used for power generation, central heating and other purposes. The circulating fluidized-bed combustion boiler 1 adapts air as the fluidizing air and oxidant;

[0052] step 2): discharging semi-coke produced by the circulating fluidized-bed gasification boiler 2 in the gasification process from the semi-coke outlet 49 back to the circulating fluidized-bed combustion boiler 1 for further combustion, discharging the synthesized gas from the top, collecting a part of particles entrained in the synthesized gas by the gasification boiler cyclone separation unit, sending the particles back into the circulating fluidized-bed gasification boiler 2 through the gasification boiler material return unit 10b for further utilization or back to the circulating fluidized-bed combustion boiler 1 for combustion. The circulating fluidized-bed gasification boiler may be set as a normal pressure system or a compression system, the operating pressure thereof is 0˜8.0 MPa, and the exit temperature of the synthesized gas reaches 650° C.˜1,050° C.;

[0053] step 3): primarily washing and de-dusting the synthesized gas, using water as a cooling media to chill the synthesized gas in a heat exchange mode and sending the cooled gas to the methanization unit by the synthesized gas purification unit, performing oil-water separation on at least one part of the sewage generated during cooling, sending impurities emitted from the separation to the combustion boiler fuel feeding opening 4a or the gasification boil fuel feeding opening 4b or for further deeper processing the at least a part of sewage as a side product;

[0054] step 4): conversing the fed synthesized gas into synthesized natural gas through low-temperature methanol washing process and methanization process, where the CH.sub.4 content in the natural gas reaches 96%; sending the carbon dioxide generated in the low-temperature methanol washing process to the gasification boiler fluidizing air inlets 11a, 11b. sending the side product—steam by the methanization process to the gasification boiler fluidizing air inlets 11a, 11b, or using it as a supplemental steam required by the methanization unit or to be expelled outside for other use.